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Knee and Thigh: Understanding the Structure and Function of the Knee Joint

Explore the complex structure of the knee joint and learn about its susceptibility to injury in athletics. Discover the role of ligaments, muscles, and neuroreceptors in providing stability. Gain insight into the patellofemoral joint and its impact on knee motion. Learn about factors affecting post-injury strength and rehabilitation concepts for knee injuries.

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Knee and Thigh: Understanding the Structure and Function of the Knee Joint

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  1. chapter23 Knee and Thigh

  2. The Knee • The knee is one of the most frequently injured joints in athletics. • The forces applied to it during sport activities are complicated by the fact that there are two long lever arms on either end of the joint, making it a joint that is susceptible to injury. • Stability comes from ligaments and muscles.

  3. Knee Structure • Two joints: tibiofemoral joint and patellofemoral (PF) joint • Capsule: resting = 20°-25° flexion; closed = full extension, external rotation (ER) • Ligaments: medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL), posterior cruciate (PCL) • MCL: restricts valgus stresses, ER • LCL: restricts varus stresses, internal rotation (IR) • ACL, PCL: restrict AP stresses; taut during IR (continued)

  4. Knee Structure (continued) • Neuroreceptors: in capsule, ligaments • 1° stability: ligaments; 2°= capsule, muscles • Medial/lateral meniscus: fibrocartilage screw home mechanism: flexion  extension WB: IR femur NWB: ER tibia • Muscles: quadriceps and hamstring groups, popliteus

  5. Patellofemoral Joint • Resting position: full extension • Closed position: knee flexion • Patella must glide freely for full knee motion to occur • Patella excursion is 5-7 cm • Inferior pole of patella lies at tibiofemoral joint margin • Contact between femur and patella changes through range of motion (ROM) (continued)

  6. Patellofemoral Joint (continued) • Joint reaction force: compressive force = PF quadriceps muscle and tendon resultant vector force • Contact pressure: ratio between PF joint reaction force and contact area • In closed kinetic chain, as knee flexes, contact area and compressive force increase • Force  is greater than surface , so compression increases in WB with ROM increases

  7. Figure 23.1

  8. PF Compressive Forces • Greatest patellofemoral compressive forces occur in 60°-90° positions. • Closed kinetic chain (CKC): 0° to 30° produces minimal PF stress. • Open kinetic chain (OKC): <20° (without weights) produces minimal PF stress. (continued)

  9. PF Compressive Forces (continued) • Distally attached cuff weights produce maximum patellofemoral compressive forces at 35°-45°. • Greatest tibiofemoral shear force: 15°-30°. • Machine resistance applied at the ankle reaches maximum patellofemoral compressive forces at 90°.

  10. Figure 23.4

  11. Patellar Malalignments • Patella alta: patella higher than its normal position in the patellofemoral groove • Patella baja: patella lower than its normal position in the patellofemoral groove

  12. Q-Angle • = The angle that is formed by a line from the anterior superior iliac spine (ASIS) to the middle patella and a line from the middle patella to the tibial tubercle • Normal Q-angle 10°-15° • Can change from weight bearing to non-weight bearing • Disputable evidence that it is larger in women because of pelvic structure • Pronation or a weak vastus medialis oblique (VMO) can increase the Q-angle

  13. Figure 23.2

  14. Leg Alignment • Excessive rearfoot pronation influences the patella’s alignment. • Since the lower extremity works as a CKC during most functions, malalignment in one segment affects or causes compensatory changes in another segment.

  15. Factors Affecting Postinjury Strength • Edema: inhibits quadriceps function • Pain: causes reflex withdrawal inhibition • Antalgic gait: causes weakness throughout lower extremity

  16. Rehabilitation Concepts • Extensor lag: in presence of full passive knee extension, incomplete active knee extension is secondary to quadriceps weakness. • Quadriceps force required for last 15° of extension is twice as great as for other ranges of motion because of the muscle’s reduced mechanical and physiological advantage. (continued)

  17. Rehabilitation Concepts (continued) • ACL stress in weight bearing is at least 0°-60° • ACL stress in non-weight bearing is greatest at 30°-60° and least at 60°-90° 0-60° 60-90°

  18. Figure 23.3

  19. Knee Bracing • ACL braces provide stability during low-stress loads but not during functional loads. • Knee braces may provide proprioceptive feedback. • Types: prophylactic for prevention, rehabilitative for protection, functional for stability • Custom and off-the-shelf

  20. Therex Progression • Dictated by tissue healing and response to exercise stress • Range of motion via exercise, joint mobilization, soft-tissue mobilization • Strength exercises with low-level resistance initially (continued)

  21. Therex Progression (continued) • Balance with bilateral support, progressing to unilateral static and then dynamic activities • Agility activities • Functional activities • Sport- and activity-specific exercises

  22. Soft-Tissue Mobilizations • Massage for edema, spasm • Deep-tissue releases for adhesions • Foam roller on tensor fascia latae (TFL), quadriceps or deep-tissue massage • Trigger point releases: • Quadriceps: patella from rectus femoris or vastus medialis • Popliteus: posterior knee pain • TFL: lateral thigh

  23. Figure 23.5a1

  24. Figure 23.5a2

  25. Figure 23.5a3

  26. Figure 23.5a4

  27. Figure 23.5b1

  28. Figure 23.5b2

  29. Figure 23.5b3

  30. Figure 23.7a

  31. Figure 23.7b1

  32. Figure 23.7b2

  33. Figure 23.7c

  34. Figure 23.10

  35. Figure 23.11

  36. Figure 23.12

  37. Figure 23.13a

  38. Figure 23.13b

  39. Figure 23.13c

  40. Figure 23.13d

  41. Figure 23.14

  42. Figure 23.15

  43. Figure 23.16

  44. Figure 23.17

  45. Figure 23.18

  46. Flexibility • Short-term: active versus passive • Prolonged • Age of scar tissue • Continuous passive motion (CPM) machines immediately following surgical repair

  47. Figure 23.19

  48. Figure 23.20

  49. Figure 23.22

  50. Figure 23.23

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